The present invention relates to an image reader including a read guide unit disposed on both sides of a document conveyance path, the read guide unit having an adjustable space in accordance with a thickness of a document conveyed, and relates to an image forming apparatus including such an image reader.
At a document reading position for reading a document conveyed is disposed a contact glass configured to come into contact with the document and to guide the conveyance of the document. In general, this contact glass is supported stably by a housing that accommodates an optical system therein.
In such a configuration, there is a case of dust entering the housing through a gap between the contact glass and a glass supporting portion of the housing and the dust adhering to the optical system in the housing. Such dust adhering to the optical system unfortunately may appear as black streak in a read image.
To avoid this, some conventional techniques propose a reader including a flexible dustproof member intervening between the lower face of a contact glass and a supporting portion of the contact glass and a restricting part provided at a part of a sheet guide unit to prevent the floating of the contact glass by a pressing force of the flexible member to the contact glass (see JP 2000-180994 A, for example).
Even with such a configuration in the conventional technique, in the case of an image reader provided with a read guide unit with an adjustable space in accordance with the thickness of a document conveyed, there is a case of dust entering inside a housing through a mechanism to move the read guide unit.
Such a mechanism adjusting the space in accordance with the thickness of a document conveyed is important for keeping good reading accuracy for both fixed ordinary paper and cards, but has a problem of often generating a gap in the housing corresponding to a moving stroke of the mechanism.
For dustproofing, the housing has to have an improved sealing property. A mechanism for such an improved sealing property, however, may hinder the smooth movement of members making up the housing, which may cause problems such as a failure in adjusting the space of a read guide unit appropriately or a document being caught at the read guide unit and fed in a slanting direction.
It is an object of the present invention to provide an image reader and an image forming apparatus capable of achieving an improved sealing property of a housing member to accommodate an optical system therein without impairing a space-adjusting function of a read guide with an adjustable space in accordance with the thickness of a document conveyed.